Influence of the cellulose purification process on the properties of aerogels obtained from rice straw.

Cellulose aerogels were obtained from purified rice straw cellulose fibres (CF) by applying different extraction methods: the conventional alkaline treatment (ALK) and alternative aqueous extraction based on the ultrasound combined with reflux heating (USHT) and subcritical water extraction (SWE) (160 and 180 °C). The composition and properties of the CFs were significantly affected by the purification process. The USHT treatment was as efficient as the ALK at eliminating the silica content, but the fibres maintained a notable ratio of hemicellulose (∼16 %). The SWE treatments were not so effective at removing silica (15 %) but greatly promoted the selective extraction of hemicellulose, especially at 180 °C (3 %). The CF compositional differences affected their hydrogel formation capacity and the properties of aerogels. A higher hemicellulose content in the CF led to better-structured hydrogels with better water-holding capacity, while the aerogels exhibited a more cohesive structure with thicker walls, higher porosity (99 %) and water vapour sorption capacity, but lower liquid water retention capacity (0.2 g/g). The residual silica content also interfered with the hydrogel and aerogel formation, giving rise to less structured hydrogels and more fibrous aerogels, with lower porosity (97-98 %).

Using rice straw fractions to develop reinforced, active PLA-starch bilayers for meat preservation.

Bilayers from thermoplastic corn starch (TPS) and PLA were obtained, incorporating or not rice straw (RS) valorised fractions: active extract (es) into PLA and cellulose fibres (cf) into TPS films. The films were obtained by thermoprocessing while the bilayers were obtained by thermocompression of the different monolayers (TPS-PLA, TPScf-PLA, TPS-PLAes and TPScf-PLAes). TPS conferred oxygen barrier capacity to the laminates, which was improved by the cf incorporation. The extract slightly reduced the PLA resistance but improved their oxygen barrier capacity. The tensile and barrier properties of the bilayers revealed changes in the performance of each layer associated with the interlayer compound migration. The TPScf-PLAes bags exhibited noticeable antioxidant capacity when used in meat packaging and reduced microbial counts throughout cold storage. Therefore, these bilayers have considerable potential to extend the shelf-life of meat samples, preserving their quality and safety for longer, while using RS fractions permits its valorisation.

Antioxidant starch composite films containing rice straw extract and cellulose fibres.

Antioxidant aqueous rice straw (RS) extract was obtained by a combined ultrasound-reflux heating process and cellulose fibres (CF) were purified by bleaching the extraction residue. Both fractions were incorporated into corn starch to obtain films by melt blending and compression moulding. CF (at 3 % wt.) greatly increased the elastic modulus (by 200 %) and tensile strength at break (by 100 %) while reducing film stretchability. Films with CF exhibited the greatest barrier capacity to water vapour and oxygen. The incorporation of RS extract (at 4, 6 and 8 % wt.) plasticised the film's amorphous phase, but also reinforced the matrix to a certain extent. The active films showed a high degree of UV absorption and DPPH radical scavenging capacity. Mono-dose sunflower oil bags were obtained with films with CF and RS extracts that, to a great extent, prevent oil oxidation in an accelerated oxidative test under UV radiation throughout 50 days.